The present invention relates to an ordered packing to intimately contact vapor and liquid phases ascending and descending within a column.
The prior art has provided liquid-gas mass transfer elements within columns or towers to bring ascending and descending vapor and liquid phases into intimate contact in distillation and absorption processes. Common liquid-gas mass transfer elements are sieve trays, plates and packing elements. Packing elements can be random or dumped such as the well known Rachid rings or can have a fixed or ordered structure relative to the column axes. The latter packings include structured packings, which consist of parallel metal or woven gauze sheets that can be crimped in a herringbone or sinusoidal pattern. Each of the sheets can also have an embossment. The sheets are assembled face to face so that the directions of the crimpings cross one another to provide alternate pathways for the vapor to ascend and the liquid to descend through the packing in a countercurrent direction to one another. Perforations can be provided within the sheets to permit mass transfer in a direction normal to the sheets.
In structured packings formed by vertically arranged sheets, as the liquid descends through the packing, it will, by and large, spread out along two opposite directions parallel to the sheets. Therefore, liquid flow in a direction normal to the sheets will be inhibited. The perforations provided in the sheets permit some liquid migration in a direction normal to the sheets, however, such perforations only make up less than 10% of the area provided by the sheets and hence, such migration is limited.
A further problem related to the use of any structured packing concerns the possibility of deformation of the packing due to shocks and vibrations attendant upon the transportation of a column containing structured packing to an erection site. It is this possibility of packing deformation which can limit the size of factory built packings.
The packing is normally installed in a column or tower in segments, each segment filling the diameter of the column or tower and consisting of packing material of identical orientation bounded by horizontal planes spaced apart by six or more inches. In the usual arrangement, each segment is rotated 90.degree. about its vertical axis in relation to the segments above and below, placing the vertical planes of the sheets in the adjacent segments.
As will be discussed, the present invention provides an ordered packing that inherently provides a more uniform distribution of descending liquid through the packing. Additionally, the ordered packing of the present invention is stronger than the crimped, sheet-type structured packing of the prior art to permit larger factory packed columns to be produced.